1. Field of the Invention
The present invention relates to a recording medium, particularly to a modified recording medium suitable for ink-jet recording. The present invention also relates to an image forming method by ink-jet printing with the above recording medium.
2. Related Background Art
Ink-jet printing is attracting attention because it realizes higher speed recording, color recording, and higher density recording. Ink-jet recording apparatus are widely used. For the ink-jet recording, specially designed coated-paper have been used such as those disclosed in JP-A-59-35977 and JP-A-1-135682 (xe2x80x9cJP-Axe2x80x9d herein means Japanese Patent Laid-Open Application). Such specially designed coated-paper involves problems below, although it is suitable for formation of fine and sharp images.
1. Lack of touch-feeling of plain paper,
2. Low suitability for pencil writing,
3. Liableness of powder falling-off from the coat layer,
4. Less suitability for general purpose use, or insufficient suitability for other recording method, and
5. Higher cost in comparison with plain paper.
Furthermore, for office uses, recording on readily available inexpensive general purpose paper is desired for mono-color recording and business color recording, not on an exclusive paper according to a recording system.
The plain paper type recording medium currently used for electrophotographic copying in offices is toner-transfer paper (PPC paper) such as those disclosed in JP-A-51-13244, JP-A-59-162561, and JP-A-59-191068. Such paper is not sufficiently suitable for ink-jet recording.
For ink-jet recording, the aforementioned PPC paper involves problems below.
1. Insufficient ink absorbency, which retards drying and fixation of ink especially when a large amount of ink is applied (undried or unfixed ink image being liable to be impaired by contact with another article),
2. Feathering of ink being caused along paper fibers during absorption of ink into the paper layer, which causes spreading of recorded dots, and irregular or blurred dot periphery to provide unsharp recorded characters or recorded images,
3. Running of color at a border between different colors of images, and non-uniform mixing of different colors of inks in color printing in which a plurality of colors of inks are applied successively and overlappingly before drying of each color of ink, not giving desired image quality (hereinafter such phenomenon is called xe2x80x9cbleedingxe2x80x9d),
4. Insufficient water fastness of recorded image owing to use of a water-soluble recording agent, and
5. Insufficient coloring ability of the coloring agent on paper.
To solve the above problems, various measures are taken. For example, for improvement of water fastness of recorded images, an ink-jet recording paper containing a halogenated quaternary ammonium salt or the like substance is disclosed in JP-A-56-99693. Such water-fast ink-jet recording paper, however, has remarkably low light fastness and low ozone fastness disadvantageously. For improving the water fastness and light fastness, recording paper containing a polyallylamine salt is disclosed in JP-A-61-58788. This recording paper, which contains the polyallylamine salt only without a special coat layer, tends to cause low image density and ink bleeding. For the same purpose, a recording sheet containing a two- or higher valent water-soluble metal salt and an organic cationic substance is disclosed in JP-A-4-75140. Such a recording sheet is not necessarily sufficient in coloring property and water fastness.
For ink-jet recording, on the other hand, recording media other than paper are investigated and used. Examples thereof include a recording sheet having a porous ink receiving layer on a substrate, and a recording sheet having an ink-receiving layer comprising a water-soluble or hydrophilic polymer provided on a substrate. JP-A-60-220750 discloses a recording sheet having a hydrophilic coating film composed of a water-soluble polyvinyl alcohol of saponification degree of 70 to 90 molt % formed on a polyester film.
With the progress of performances of the ink-jet recording apparatus in recording speed, color printing, printing density, and so forth, the aforementioned recording sheets employing a plastic base other than paper are also required to have higher levels of properties to provide recording images of high resolution and high image quality similarly as recording paper, as below.
1. High ink absorbency to provide rapid drying and fixation of ink,
2. No bleeding, namely no flowing-out of ink to an adjacent ink dot, not to cause irregular mixing of the ink even when ink dots are formed adjacently,
3. No beading caused (xe2x80x9cbeadingxe2x80x9d means irregular optical density in a bead-like form caused by agglomeration of a dye on an ink receiving layer),
4. No excessive spreading of ink dot diameter caused by diffusion of an applied ink droplet on a recording sheet,
5. High image density formed by ink dots, and no blurring of periphery of recorded characters or images,
6. High coloring property of coloring component of ink,
7. High reproducibility of color, and high fineness of printed image,
8. High water fastness, and so forth.
Of the above required properties, water fastness is especially important. JP-A-1-190483 discloses an ink-jet recording sheet having improved water fastness of recorded images. Such disclosed types of recording sheets are not satisfactory in other ink-jet recording properties, e.g., ink-fixing properties, image density, sharpness of recorded images, etc.
The present invention intends to provide a recording medium, especially an ink-jet recording medium having the properties below:
1. Sufficient fixability for ink, and capability of giving excellent and high quality of characters,
2. Capability of giving sufficient image density and uniform solid print images,
3. No bleeding in color image formation,
4. Sufficient color reproducibility, and capability of giving sharp images in color image formation,
5. Capability of giving complete water fastness to recorded images, and so forth; and also intends to provide image forming method employing the recording medium.
The present invention further intends to provide a recording paper which has the above properties, has touch-feeling like plain paper, are useful commonly for various recording method including electrophotographic recording, thermal transfer recording, impact recording, and ink-jet recording, and are useful also for writing with a pencil, a felt pen, or a ball-point pen; and also intends to provide an image forming method employing the above recording paper.
The present invention still further intends to provide a recording medium employing a base material other than paper, and having the above-mentioned properties, and also intends to provide an image forming method employing the above recording sheet.
The objects mentioned above can be achieved by the present invention.
According to the present invention, there is provided a recording method for image formation on a recording medium by application thereon of an ink containing a water soluble dye having an anionic group or a cationic group, the recording medium comprising a substance having an ionic group counter to the anionic or cationic group of the water-soluble dye and having molecular weight of not higher than 1,000, and a polymeric substance having molecular weight of not lower than 2,000.
According to the present invention, there is still provided a recording medium of the present invention comprises a substance having molecular weight of not higher than 1,000 selected from the group consisting of organic cationic substances, basic polyaluminum chloride, and a basic aluminum salt of an organic acid; and a cationic polymeric substance having molecular weight of not less than 2,000.
According to the present invention there is further provided an image-forming method, comprising applying an ink containing at least a water-soluble dye having an anionic group in the molecule onto a recording paper medium specified above.